The first female Prime Minister of the United Kingdom was Margaret Thatcher. Serving from 1979 to 1990, she was the leader of the Conservative Party and famously known as the "Iron Lady," a nickname that reflected her strong, uncompromising leadership style. Thatcher implemented significant economic reforms, focusing on reducing the power of trade unions, privatizing state-owned industries, and promoting free-market policies. Her government faced challenges, including economic recession and social unrest, yet she remains a pivotal figure in British politics. Thatcher's legacy is debated; supporters praise her economic revival efforts, while critics argue that her policies increased inequality.